/*
 * Copyright 2013 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package io.netty.buffer;

import io.netty.util.ByteProcessor;
import io.netty.util.internal.EmptyArrays;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.StringUtil;

import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.ReadOnlyBufferException;
import java.nio.channels.FileChannel;
import java.nio.channels.GatheringByteChannel;
import java.nio.channels.ScatteringByteChannel;
import java.nio.charset.Charset;

/**
 * An empty {@link ByteBuf} whose capacity and maximum capacity are all
 * {@code 0}.
 */
public final class EmptyByteBuf extends ByteBuf
{

    private static final ByteBuffer EMPTY_BYTE_BUFFER = ByteBuffer
            .allocateDirect(0);

    private static final long EMPTY_BYTE_BUFFER_ADDRESS;

    static
    {
        long emptyByteBufferAddress = 0;
        try
        {
            if (PlatformDependent.hasUnsafe())
            {
                emptyByteBufferAddress = PlatformDependent
                        .directBufferAddress(EMPTY_BYTE_BUFFER);
            }
        }
        catch (Throwable t)
        {
            // Ignore
        }
        EMPTY_BYTE_BUFFER_ADDRESS = emptyByteBufferAddress;
    }

    private final ByteBufAllocator alloc;

    private final ByteOrder order;

    private final String str;

    private EmptyByteBuf swapped;

    public EmptyByteBuf(ByteBufAllocator alloc)
    {
        this(alloc, ByteOrder.BIG_ENDIAN);
    }

    private EmptyByteBuf(ByteBufAllocator alloc, ByteOrder order)
    {
        if (alloc == null)
        {
            throw new NullPointerException("alloc");
        }

        this.alloc = alloc;
        this.order = order;
        str = StringUtil.simpleClassName(this)
                + (order == ByteOrder.BIG_ENDIAN ? "BE" : "LE");
    }

    @Override
    public int capacity()
    {
        return 0;
    }

    @Override
    public ByteBuf capacity(int newCapacity)
    {
        throw new ReadOnlyBufferException();
    }

    @Override
    public ByteBufAllocator alloc()
    {
        return alloc;
    }

    @Override
    public ByteOrder order()
    {
        return order;
    }

    @Override
    public ByteBuf unwrap()
    {
        return null;
    }

    @Override
    public ByteBuf asReadOnly()
    {
        return Unpooled.unmodifiableBuffer(this);
    }

    @Override
    public boolean isReadOnly()
    {
        return false;
    }

    @Override
    public boolean isDirect()
    {
        return true;
    }

    @Override
    public int maxCapacity()
    {
        return 0;
    }

    @Override
    public ByteBuf order(ByteOrder endianness)
    {
        if (endianness == null)
        {
            throw new NullPointerException("endianness");
        }
        if (endianness == order())
        {
            return this;
        }

        EmptyByteBuf swapped = this.swapped;
        if (swapped != null)
        {
            return swapped;
        }

        this.swapped = swapped = new EmptyByteBuf(alloc(), endianness);
        return swapped;
    }

    @Override
    public int readerIndex()
    {
        return 0;
    }

    @Override
    public ByteBuf readerIndex(int readerIndex)
    {
        return checkIndex(readerIndex);
    }

    @Override
    public int writerIndex()
    {
        return 0;
    }

    @Override
    public ByteBuf writerIndex(int writerIndex)
    {
        return checkIndex(writerIndex);
    }

    @Override
    public ByteBuf setIndex(int readerIndex, int writerIndex)
    {
        checkIndex(readerIndex);
        checkIndex(writerIndex);
        return this;
    }

    @Override
    public int readableBytes()
    {
        return 0;
    }

    @Override
    public int writableBytes()
    {
        return 0;
    }

    @Override
    public int maxWritableBytes()
    {
        return 0;
    }

    @Override
    public boolean isReadable()
    {
        return false;
    }

    @Override
    public boolean isWritable()
    {
        return false;
    }

    @Override
    public ByteBuf clear()
    {
        return this;
    }

    @Override
    public ByteBuf markReaderIndex()
    {
        return this;
    }

    @Override
    public ByteBuf resetReaderIndex()
    {
        return this;
    }

    @Override
    public ByteBuf markWriterIndex()
    {
        return this;
    }

    @Override
    public ByteBuf resetWriterIndex()
    {
        return this;
    }

    @Override
    public ByteBuf discardReadBytes()
    {
        return this;
    }

    @Override
    public ByteBuf discardSomeReadBytes()
    {
        return this;
    }

    @Override
    public ByteBuf ensureWritable(int minWritableBytes)
    {
        if (minWritableBytes < 0)
        {
            throw new IllegalArgumentException("minWritableBytes: "
                    + minWritableBytes + " (expected: >= 0)");
        }
        if (minWritableBytes != 0)
        {
            throw new IndexOutOfBoundsException();
        }
        return this;
    }

    @Override
    public int ensureWritable(int minWritableBytes, boolean force)
    {
        if (minWritableBytes < 0)
        {
            throw new IllegalArgumentException("minWritableBytes: "
                    + minWritableBytes + " (expected: >= 0)");
        }

        if (minWritableBytes == 0)
        {
            return 0;
        }

        return 1;
    }

    @Override
    public boolean getBoolean(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public byte getByte(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public short getUnsignedByte(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public short getShort(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public short getShortLE(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int getUnsignedShort(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int getUnsignedShortLE(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int getMedium(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int getMediumLE(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int getUnsignedMedium(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int getUnsignedMediumLE(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int getInt(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int getIntLE(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public long getUnsignedInt(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public long getUnsignedIntLE(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public long getLong(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public long getLongLE(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public char getChar(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public float getFloat(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public double getDouble(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf getBytes(int index, ByteBuf dst)
    {
        return checkIndex(index, dst.writableBytes());
    }

    @Override
    public ByteBuf getBytes(int index, ByteBuf dst, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public ByteBuf getBytes(int index, ByteBuf dst, int dstIndex, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public ByteBuf getBytes(int index, byte[] dst)
    {
        return checkIndex(index, dst.length);
    }

    @Override
    public ByteBuf getBytes(int index, byte[] dst, int dstIndex, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public ByteBuf getBytes(int index, ByteBuffer dst)
    {
        return checkIndex(index, dst.remaining());
    }

    @Override
    public ByteBuf getBytes(int index, OutputStream out, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public int getBytes(int index, GatheringByteChannel out, int length)
    {
        checkIndex(index, length);
        return 0;
    }

    @Override
    public int getBytes(int index, FileChannel out, long position, int length)
    {
        checkIndex(index, length);
        return 0;
    }

    @Override
    public CharSequence getCharSequence(int index, int length, Charset charset)
    {
        checkIndex(index, length);
        return null;
    }

    @Override
    public ByteBuf setBoolean(int index, boolean value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setByte(int index, int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setShort(int index, int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setShortLE(int index, int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setMedium(int index, int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setMediumLE(int index, int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setInt(int index, int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setIntLE(int index, int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setLong(int index, long value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setLongLE(int index, long value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setChar(int index, int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setFloat(int index, float value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setDouble(int index, double value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setBytes(int index, ByteBuf src)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf setBytes(int index, ByteBuf src, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public ByteBuf setBytes(int index, ByteBuf src, int srcIndex, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public ByteBuf setBytes(int index, byte[] src)
    {
        return checkIndex(index, src.length);
    }

    @Override
    public ByteBuf setBytes(int index, byte[] src, int srcIndex, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public ByteBuf setBytes(int index, ByteBuffer src)
    {
        return checkIndex(index, src.remaining());
    }

    @Override
    public int setBytes(int index, InputStream in, int length)
    {
        checkIndex(index, length);
        return 0;
    }

    @Override
    public int setBytes(int index, ScatteringByteChannel in, int length)
    {
        checkIndex(index, length);
        return 0;
    }

    @Override
    public int setBytes(int index, FileChannel in, long position, int length)
    {
        checkIndex(index, length);
        return 0;
    }

    @Override
    public ByteBuf setZero(int index, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public int setCharSequence(int index, CharSequence sequence,
            Charset charset)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public boolean readBoolean()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public byte readByte()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public short readUnsignedByte()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public short readShort()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public short readShortLE()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int readUnsignedShort()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int readUnsignedShortLE()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int readMedium()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int readMediumLE()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int readUnsignedMedium()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int readUnsignedMediumLE()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int readInt()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int readIntLE()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public long readUnsignedInt()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public long readUnsignedIntLE()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public long readLong()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public long readLongLE()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public char readChar()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public float readFloat()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public double readDouble()
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf readBytes(int length)
    {
        return checkLength(length);
    }

    @Override
    public ByteBuf readSlice(int length)
    {
        return checkLength(length);
    }

    @Override
    public ByteBuf readRetainedSlice(int length)
    {
        return checkLength(length);
    }

    @Override
    public ByteBuf readBytes(ByteBuf dst)
    {
        return checkLength(dst.writableBytes());
    }

    @Override
    public ByteBuf readBytes(ByteBuf dst, int length)
    {
        return checkLength(length);
    }

    @Override
    public ByteBuf readBytes(ByteBuf dst, int dstIndex, int length)
    {
        return checkLength(length);
    }

    @Override
    public ByteBuf readBytes(byte[] dst)
    {
        return checkLength(dst.length);
    }

    @Override
    public ByteBuf readBytes(byte[] dst, int dstIndex, int length)
    {
        return checkLength(length);
    }

    @Override
    public ByteBuf readBytes(ByteBuffer dst)
    {
        return checkLength(dst.remaining());
    }

    @Override
    public ByteBuf readBytes(OutputStream out, int length)
    {
        return checkLength(length);
    }

    @Override
    public int readBytes(GatheringByteChannel out, int length)
    {
        checkLength(length);
        return 0;
    }

    @Override
    public int readBytes(FileChannel out, long position, int length)
    {
        checkLength(length);
        return 0;
    }

    @Override
    public CharSequence readCharSequence(int length, Charset charset)
    {
        checkLength(length);
        return null;
    }

    @Override
    public ByteBuf skipBytes(int length)
    {
        return checkLength(length);
    }

    @Override
    public ByteBuf writeBoolean(boolean value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeByte(int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeShort(int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeShortLE(int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeMedium(int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeMediumLE(int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeInt(int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeIntLE(int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeLong(long value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeLongLE(long value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeChar(int value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeFloat(float value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeDouble(double value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeBytes(ByteBuf src)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public ByteBuf writeBytes(ByteBuf src, int length)
    {
        return checkLength(length);
    }

    @Override
    public ByteBuf writeBytes(ByteBuf src, int srcIndex, int length)
    {
        return checkLength(length);
    }

    @Override
    public ByteBuf writeBytes(byte[] src)
    {
        return checkLength(src.length);
    }

    @Override
    public ByteBuf writeBytes(byte[] src, int srcIndex, int length)
    {
        return checkLength(length);
    }

    @Override
    public ByteBuf writeBytes(ByteBuffer src)
    {
        return checkLength(src.remaining());
    }

    @Override
    public int writeBytes(InputStream in, int length)
    {
        checkLength(length);
        return 0;
    }

    @Override
    public int writeBytes(ScatteringByteChannel in, int length)
    {
        checkLength(length);
        return 0;
    }

    @Override
    public int writeBytes(FileChannel in, long position, int length)
    {
        checkLength(length);
        return 0;
    }

    @Override
    public ByteBuf writeZero(int length)
    {
        return checkLength(length);
    }

    @Override
    public int writeCharSequence(CharSequence sequence, Charset charset)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public int indexOf(int fromIndex, int toIndex, byte value)
    {
        checkIndex(fromIndex);
        checkIndex(toIndex);
        return -1;
    }

    @Override
    public int bytesBefore(byte value)
    {
        return -1;
    }

    @Override
    public int bytesBefore(int length, byte value)
    {
        checkLength(length);
        return -1;
    }

    @Override
    public int bytesBefore(int index, int length, byte value)
    {
        checkIndex(index, length);
        return -1;
    }

    @Override
    public int forEachByte(ByteProcessor processor)
    {
        return -1;
    }

    @Override
    public int forEachByte(int index, int length, ByteProcessor processor)
    {
        checkIndex(index, length);
        return -1;
    }

    @Override
    public int forEachByteDesc(ByteProcessor processor)
    {
        return -1;
    }

    @Override
    public int forEachByteDesc(int index, int length, ByteProcessor processor)
    {
        checkIndex(index, length);
        return -1;
    }

    @Override
    public ByteBuf copy()
    {
        return this;
    }

    @Override
    public ByteBuf copy(int index, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public ByteBuf slice()
    {
        return this;
    }

    @Override
    public ByteBuf retainedSlice()
    {
        return this;
    }

    @Override
    public ByteBuf slice(int index, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public ByteBuf retainedSlice(int index, int length)
    {
        return checkIndex(index, length);
    }

    @Override
    public ByteBuf duplicate()
    {
        return this;
    }

    @Override
    public ByteBuf retainedDuplicate()
    {
        return this;
    }

    @Override
    public int nioBufferCount()
    {
        return 1;
    }

    @Override
    public ByteBuffer nioBuffer()
    {
        return EMPTY_BYTE_BUFFER;
    }

    @Override
    public ByteBuffer nioBuffer(int index, int length)
    {
        checkIndex(index, length);
        return nioBuffer();
    }

    @Override
    public ByteBuffer[] nioBuffers()
    {
        return new ByteBuffer[]
        { EMPTY_BYTE_BUFFER };
    }

    @Override
    public ByteBuffer[] nioBuffers(int index, int length)
    {
        checkIndex(index, length);
        return nioBuffers();
    }

    @Override
    public ByteBuffer internalNioBuffer(int index, int length)
    {
        return EMPTY_BYTE_BUFFER;
    }

    @Override
    public boolean hasArray()
    {
        return true;
    }

    @Override
    public byte[] array()
    {
        return EmptyArrays.EMPTY_BYTES;
    }

    @Override
    public int arrayOffset()
    {
        return 0;
    }

    @Override
    public boolean hasMemoryAddress()
    {
        return EMPTY_BYTE_BUFFER_ADDRESS != 0;
    }

    @Override
    public long memoryAddress()
    {
        if (hasMemoryAddress())
        {
            return EMPTY_BYTE_BUFFER_ADDRESS;
        }
        else
        {
            throw new UnsupportedOperationException();
        }
    }

    @Override
    public String toString(Charset charset)
    {
        return "";
    }

    @Override
    public String toString(int index, int length, Charset charset)
    {
        checkIndex(index, length);
        return toString(charset);
    }

    @Override
    public int hashCode()
    {
        return 0;
    }

    @Override
    public boolean equals(Object obj)
    {
        return obj instanceof ByteBuf && !((ByteBuf) obj).isReadable();
    }

    @Override
    public int compareTo(ByteBuf buffer)
    {
        return buffer.isReadable() ? -1 : 0;
    }

    @Override
    public String toString()
    {
        return str;
    }

    @Override
    public boolean isReadable(int size)
    {
        return false;
    }

    @Override
    public boolean isWritable(int size)
    {
        return false;
    }

    @Override
    public int refCnt()
    {
        return 1;
    }

    @Override
    public ByteBuf retain()
    {
        return this;
    }

    @Override
    public ByteBuf retain(int increment)
    {
        return this;
    }

    @Override
    public ByteBuf touch()
    {
        return this;
    }

    @Override
    public ByteBuf touch(Object hint)
    {
        return this;
    }

    @Override
    public boolean release()
    {
        return false;
    }

    @Override
    public boolean release(int decrement)
    {
        return false;
    }

    private ByteBuf checkIndex(int index)
    {
        if (index != 0)
        {
            throw new IndexOutOfBoundsException();
        }
        return this;
    }

    private ByteBuf checkIndex(int index, int length)
    {
        if (length < 0)
        {
            throw new IllegalArgumentException("length: " + length);
        }
        if (index != 0 || length != 0)
        {
            throw new IndexOutOfBoundsException();
        }
        return this;
    }

    private ByteBuf checkLength(int length)
    {
        if (length < 0)
        {
            throw new IllegalArgumentException(
                    "length: " + length + " (expected: >= 0)");
        }
        if (length != 0)
        {
            throw new IndexOutOfBoundsException();
        }
        return this;
    }
}
